bug#24665: 25.1; Confusing documentation of Tramp methods

[Eli Zaretskii <eliz@gnu.org>]

The Tramp manual says in the node External Methods:

  ‘scp’—‘ssh’ and ‘scp’

       Using a combination of ‘ssh’ to connect and ‘scp’ to transfer is
       the most secure.  While the performance is good, it is slower than
       the inline methods for smaller files.  Though there is no overhead
       of encoding and decoding of the inline methods, ‘scp’’s
       cryptographic handshake negates those speed gains.
  [...]

  ‘pscp’—‘plink’ and ‘pscp’
  ‘psftp’—‘plink’ and ‘psftp’

       These methods are similar to ‘scp’ or ‘sftp’, but they use the
       ‘plink’ command to connect to the remote host, and they use ‘pscp’
       or ‘psftp’ for transferring the files.  These programs are part of
       PuTTY, an SSH implementation for Windows.

This seems to say that a file name like the following should work:

  /pscp-plink:username@hostname:filename

But in reality, Tramp says 'Unknown method "pscp-plink"'.  Using just
"pscp" does work.

So it seems like the above doesn't mean to say I should use
"pscp-plink" literally.  But what _does_ it mean?  I didn't find any
clues neither in the Tramp manual nor in the doc string of
tramp-methods.


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